One characteristic of LED lamps is that high power light output correlates with high heat generation, and the need for heat sinks or other techniques for dissipation and radiation of this heat. Unfortunately, because heat dissipation is currently a major challenge, heat sinks for LED lamps often have a significant amount of mass, and thus, weight Accordingly, such limitations detract from the utility of the resulting lamps.
One approach considered has been to increase the size of the heat sink for a given lamp configuration, however, in conventional embodiments, large heat sinks can reduce the utility of an LED lamp (see examples below). Another approach has been to improve efficiency for light output such that a lamp can have a high ratio of light output to mass of the heat sink. This has been an elusive goal, until the advent of techniques disclosed herein.
Having small heat sinks with a high ratio of light output to mass is especially important for the case where LEDs lamps are placed in lighting enclosures that have poor air circulation. A typical example is a recessed ceiling enclosure, where the temperature can be over 50 degrees C. At such, temperatures, the emissivity of heat sink surfaces plays only a small role in dissipating heat. Therefore, other techniques must be used for dissipation and radiation of heat generated by high power light outputting devices. Additionally, because conventional electronic assembly techniques and LED reliability factors limit printed circuit board temperatures to no greater than about 85 degrees C., the power output of the LEDs is also constrained by heat dissipation. Still further, because total light output from LED lighting sources can be increased by simply increasing the number of LEDs, this has led to increased device costs, increased device size, and increased weight of the LED illumination source.
Although lighter weight LED illumination sources are desired, for at least the aforementioned reasons, conventional light sources typically use large passive heat sinks (sometimes massive heat sinks). Further, smaller LED illumination sources are also desired, yet, for at least the aforementioned reasons, conventional sources use larger-than-needed form factors.